It’s funny to hear someone say it is “very rigid beliefs” to disagree with dogmatically using auto everywhere just to get polymorphism by swapping header files, which is a far more drastic and brittle belief.

I have worked on systems deploying to embedded devices, so I am familiar with e.g. needing to suddenly change a bunch of code to cause some typedef to refer to int16 because a platform doesn’t support int32, and needing the codebase to be robust to the change. Whatever solution you pick, sacrificing localized explicit type info is not a good trade-off, and ability to read code and locally easily reason about types only gets more critical as the application gets more architecture or performance dependent.

Besides, many systems that need to achieve this same effect do so by either using discriminated union (std::variant) and multiple dispatch patterns, or by designing the different specific subtypes to fit into an inheritance hierarchy, so that switching things to use e.g. different integer precisions is a matter of using a different, specialized subtype. Forcing the use of auto everywhere and switching types by header files would be a nuclear option by comparison.